The Hippopotamus at the Regent's Park Zoo, ca. 1855. Photo by Juan, Count of Montizón.

Don Juan Carlos María Isidro de Borbón, Count of Montizón (French: Jean Charles Marie Isidore de Bourbon, comte de Montizón) (May 15, 1822 – November 18, 1887) was the Carlist claimant to the throne of Spain from 1860 to 1868, and the Legitimist claimant to the throne of France from 1883 to 1887.

In March 1833 Juan moved with his family to Portugal. The following September Juan's uncle Ferdinand VII died, and Juan's father Carlos claimed the throne of Spain as King Carlos V. Carlos opposed the succession of his infant niece Queen Isabella II whose mother the Queen Regent Maria Christina managed to take control on behalf of her daughter. In June 1834 Juan moved with his family to England where they lived at Gloucester Lodge, Old Brompton Road, and later at Alverstoke Old Rectory, Hampshire. He remained in England throughout the First Carlist War, playing no part in it on account of his youth.

On January 15, 1837 the Cortes which was controlled by the Isabellists passed a law, ratified by the Queen Regent Maria Christina, which excluded Juan, his father, and brothers from the Spanish succession. By the same law the title of Infante of Spain was removed from Juan and his family. From the perspective of the Carlists this law was invalid.

Juan and Beatrix lived first in Modena, but had to leave during the revolution of 1848. After a brief time in Austria, they settled in London where their younger son was born. In spite of the conservatism and religious piety of his own family and particularly that of his wife, Juan developed liberal tendencies. He separated from his wife who returned to Modena where she raised her two sons. Juan was an active photographer and a founder member of the Photographic Society (later the Royal Photographic Society) from 1853 and is last recorded as a member in 1866.[1]

Juan played no part in the 1860 Carlist rising led by his brother Carlos Luis, count of Montemolín. On April 21 Carlos Luis was captured by the troops of Isabella II and forced to renounce his claims to the Spanish throne. On June 2 Juan published a declaration affirming his accession as Juan III, King of Spain;[2] henceforward he used the title conde de Montizón (in commemoration of a commandery of the Order of Santiago which belonged to his father). Juan's accession declaration used phrases such as "the light and progress of the age"; these phrases caused great offence to many Carlists most of whom refused to support him.

Once he had left Spain, his brother Carlos Luis renounced his abdication. On June 15 he declared that it was invalid since he had been forced to sign against his will.[3] Juan refused to accept his brother's declaration. Until the unexpected death of Carlos Luis the following January, there were two Carlist claimants.

During the early 1860s the popularity of the government of Isabella II continued to decline. Juan's liberal views, however, ensured that he was not a viable candidate for the Carlists. In 1866, Juan's elder son Carlos (now aged eighteen) asked his father to abdicate his rights, but he did nothing.[4] Two years later, however, on October 3, 1868, Juan signed a decree of abdication at Paris.[5] He became an active supporter of his son Carlos' attempts to regain the Spanish throne in the Third Carlist War.

After his abdication Juan lived mostly in England in the town of Worthing. He used the name Charles Monfort. He lived with an English woman, Ellen Sarah Carter, with whom he had a son John Monfort (1861–1929) and a daughter Helen (1859–1947)

On August 24, 1883 Juan's distant cousin (paternal nephew) and brother-in-law Henri, comte de Chambord died. Henri had been the Legitimist claimant to the throne of France. Henri's widow, Archduchess Maria Theresa of Austria-Este, and a minority of his supporters held that Juan as senior male descendant of Louis XIV was his successor. They proclaimed him as Jean III, King of France and Navarre. He issued a declaration saying, "Having become Head of the House of Bourbon by the death of my brother-in-law and cousin, the Comte de Chambord, I declare that I do not in any way renounce the rights to the throne of France which I have held since my birth". But other than this declaration he made no active claim to the French throne.

Juan died of angina at his home (25 Seafield Road) in Hove on Friday 18 November 1887. His death was registered by an Ellen Sarah Carter. His body was moved to the Church of the Sacred Heart, Norton Road, Hove on the 20th of November, where he lay in state until his funeral mass was held on the 24th November in the presence of his two sons; Don Carlos, Duke of Madrid and Don Alfonso, Duke of San Jaime.[6]

His body was moved on the 6 January 1888 from Hove to St Katherine's Dock London along with the body of his Mother, Queen Maria Francisa, who had been buried at the Roman Catholic Church of our Lady, Gosport, where she had been laid to rest in September 1834. The bodies left aboard the General Steamship Navigation Company's vessel on the 7 January bound for Hamburg and then via Berlin and Vienna and on to Trieste where it is buried in the chapel of Saint Charles Borromeo in Trieste Cathedral.[7] The inscription on his tomb names him as the King of Spain.

The generations indicate descent from Carlos I, under whom the crowns of Castile and Aragon were united, forming the Kingdom of Spain. Previously, the title Infante had been largely used in the different realms.